In 1997 the young historian Iris Chang grabbed America's attention with her often gruesome book The Rape of Nanking: the forgotten holocaust of World War II, which explained the still latent hatred of the Chinese against the Japanese. It told the story of the cold-blooded massacre in 1937 by the Japanese of between 260,000 and 400,000 Chinese soldiers and civilians after the fall of the Kuomintang (KMT) capital of China.

In 1997 the young historian Iris Chang grabbed America's attention with her often gruesome book The Rape of Nanking: the forgotten holocaust of World War II, which explained the still latent hatred of the Chinese against the Japanese. It told the story of the cold-blooded massacre in 1937 by the Japanese of between 260,000 and 400,000 Chinese soldiers and civilians after the fall of the Kuomintang (KMT) capital of China.

The book became an unexpected US bestseller. Although for the scholarly community it contained few new facts, it managed to bring home the utter barbarity of the Japanese and the humiliation of the Chinese in an episode that has largely been forgotten in the rest of the world.

Although it was well-documented at the time by the few dozen foreigners living in Nanking who managed to save hundreds of thousands of lives by giving shelter in the international zone, and at the war crimes trials after Japan's defeat, it subsequently received little attention. Japan has tried to ignore or downplay events in Nanking and has never satisfactorily apologised for its behaviour. Japanese school textbooks barely mention it.

The continuing annual pilgrimage made by Japanese politicians to the Yasukuni Shrine in Tokyo to honour the perpetrators of the massacre infuriates China, and the refusal of Japan's current prime minister Junichiro Koizumi to stop going to the shrine has brought about a new freeze in Japanese and Chinese relations.

Iris Chang was born in Princeton, New Jersey, in 1968, the daughter of a physics professor and a microbiologist. Her first book, Thread of the Silkworm (1995), described how China acquired its missile technology through the defection of an influential American of Chinese descent.

After her parents told her the story of her grandparents' flight from Nanking as the Japanese marched in, she began to interview other survivors in America. "I was walking around in a state of shock," Chang said later, at the horror of what they described.

Among her discoveries was the role of John Rabe, a Nazi businessman who had stayed behind in Nanking, in helping to organise an extraordinary effort to bluff the Japanese into recognising the international sanctuary. Acting on a hunch, Chang tracked down Rabe's granddaughter in Germany and his diary came to light for the first time. It recorded his horrified reaction to the mass rapes, torture and executions he witnessed. The diary confirmed that the worst allegations by Chinese victims, routinely given huge prominence in the Chinese media, are true.

"This is a book I really had to write," Chang said in an interview. "I wrote it out of a sense of rage. I didn't really care if I made a cent from it. It was important to me that the world knew what happened in Nanking back in 1937."

Her third book, The Chinese in America (2003), looked at the history of Chinese immigrants in the United States. She had been working on a fourth book, about the terrible experiences of men in the US tank battalions who were captured in the Bataan Peninsula in the Philippines and their subsequent imprisonment by the Japanese.

About five months ago, Iris Chang suffered a mental breakdown during a research trip and continued to battle depression. Last week she was found dead from gunshot wounds. Police reports said she had committed suicide.